The primary objective of the present invention is to provide a lithium secondary battery having high energy density and excellent charging/discharging cycle characteristic, capable of restraining further oxidation decompounding on a surface of a positive electrode active material even when deoxidized/decompounded products of non-aqueous electrolyte generated on the surface of silicon negative electrode active material in charging/discharging is dispersed and moved to the positive electrode. The lithium secondary battery has a positive electrode (1) containing a positive electrode active material having particles of lithium cobalt oxide, a negative electrode (2) containing a negative electrode active material having silicon particles, a separator (3) interposed between the positive electrode (1) and the negative electrode (2), and a non-aqueous electrolyte. Particles of erbium hydroxide or erbium oxyhydroxide are adhered to a surface of the lithium cobalt oxide particles in a dispersed form.